Image or picture projection devices have a plurality of systems. In a projection device using a phase modulation type spatial modulation element, which is one of them, a laser is used as a light source, and a laser light is diffracted on the basis of information of each pixel to form an image. Thus, a light can be concentrated on only a desired part, and an image or a picture can be projected brightly.
However, in such a system, since a laser is used as a light source, measures to ensure safety need to be implemented.
Patent Literature 1 (PTL1) states that a ratio of power of laser lights emitted from light sources of respective colors is obtained according to an image signal, and the laser lights emitted from the light sources are adjusted according to the obtained ratio such that a projection light does not exceed the upper limit of safety standards.